Conventional grids of the type here contemplated include a multiplicity of mutually parallel and equispaced profiled bars, interlinked by transverse connector elements with coupling formations engaged in complementary, undercut grooves of the bars, and tread-supporting or carrier strips of yieldable material such as felt, textile fabric, rubber or bristles which are received in rails of stiffly resilient polymeric material, specifically hard plastic. The rails are thin-walled profiles of generally U-shaped cross-section and interlockingly engage in undercut upwardly open longitudinal channels of respective bars whereby the tread-supporting strips jointly define the upper mat surface.
Such grids, with the complementary grooves formed on the undersides of the bars, are known from my German Pat. No. 24 12 151 and printed specification No. 27 19 857. They have the advantage of convenient assembly and are therefore suitable for manufacture in workshops manned by handicapped personnel.
A drawback of this type of construction resides in the considerable height of the resulting mat which is due to the fact that the grooves accommodating the coupling formations of the connector elements lie well below the levels of the upwardly open channels receiving the strip-supporting rails. In some instances, therefore, the mats can be used only on a suitably recessed floor. While the height of the mat can be reduced by providing the undercut coupling grooves on the sides of the bars rather than on their lower surfaces, as suggested in German published application No. 31 24 529, that solution results in a significant broadening of each bar; besides, the assembly of the parts requires an endwise introduction of the coupling formations into the associated grooves which creates problems for handicapped persons assigned to this task.